Healthy lifestyle choices—exercising, eating well, going outside, pretty much all the things mami told you do—really can make you feel happier.

Get some sun

Get some sun

New Milford, Connecticut, nanny Melissa Nercessian often works indoors during the day. "I grew up in Puerto Rico," she says, "and in San Juan, I practically lived at the beach." After her doctor diagnosed her with Seasonal Affective Disorder (SAD), Nercessian started taking a daily walk outside at lunchtime. Since a lack of sun has been linked to depression, "Try to get sun on your face every day before noon," suggests Dr. Belisa Vranich, coauthor of The Seven Beliefs.

Keep a gratitutde journal, or pay it forward

Keep a gratitutde journal, or pay it forward

Abuelita was right: You should count your blessings. Recent research suggests that doing so once a day can have a long-term effect on keeping depression away. How? It focuses you away from what's wrong in your life and toward what's right. Helping somebody out is also effective. "It reminds you that lots of other people are worse off than you are—and that you have the power to make things better," says Araceli Sanchez, a tax preparer who volunteers as a counselor at her Florida City church at least once a week.